Cnidaria

Class Hydrozoa

-Actually only one species thought to be immortal -Hydra is immortal -Medusa stage reverts to polyp when damages, restarts life cycle -Can still die from injuries, predation etc.

Medusa

-Adult phase of the jellyfish lifecycle -motile -sexual stage of organism

Class Scyphozoa

-Aurelia, true jellies -Prey consists of crustaceans, fish -Bell can be contracted to swim through water

Cnidaria - Importance

-Colonial forms form vast coral reefs of CaCO3 (calcium carbonate) -Coral reefs are among the most productive ecosystems on Earth -Reefs support commercial fisheries around the world -Reef fish and invertebrates are harvested for the aquarium pet trade

Phylum Ctenophora

-Comb jellies - once classed with cnidarians in the Phylum Coelentrata -Similar to jellyfish, but: Simpler life cycle Lack nematocysts, capture prey with sticky cells on two long tentacles Combs of cilia beat in sequence to move the jelly around - beautiful to see!!

Gastrovascular Cavity (GVC)

-Digestion is extracellular -Gland cells break down food in the GVC -Can eat things larger than their cells (Carnivorous)

Cnidarian Body Plan

-Only two of the three eumetazoan tissue layers - ectoderm, endoderm, but no mesoderm

Umbrella (bell)

-Part of the jellyfish which the tentacles extend from

Class Cubozoa

-Sea wasps - 20 species -Among the deadliest animals on Earth!! -Over 50 fatalities recorded from Australia, death occurs in 3-20 minutes!!

Cnidocytes

-Stinging cells called ____________ contain coiled nematocysts -Cell membrane of ____________ responds to chemical or mechanical stimuli (touch) -Cell membrane changes permeability -Water rushes in, explodes nematocyst out at 40 atmospheres of osmotic pressure! -Discharge without additional energy

Phylum Cnidaria

-Subkingdom Eumetazoa -Radially symmetric animals - Radiata -Phylum Cnidaria - hydrozoans, coral, anemones -Mostly marine, some freshwater -Carnivorous - capture live prey -Sessile and motile (dimorphic)- first fully motile animals -Cnidarians were the first animals to develop a gut cavity (GVC) -Cnidarians are the first animals to develop differentiated tissues -Cnidarians were the first truly mobile creatures

Cnidarian Nervous System

-These muscles are controlled by the first true nerve cells -True nerve cells, but no CNS, just a simple nerve net (why??) -Not motile, therefor there is no need to develop a centralized nerve system, or head.

Polyp

-Young phase of the jellyfish lifecycle -sessile -Polyp is the dominant stage in the life cycle -Polyp tentacles lined with cnidocytes

Budding

-a sexual reproduction by polyps

Nematocysts

-coiled within cnidocytes -Different types 1) Sticky threads, used for attachment, or moving short distances 2) Long coils that whip around the prey and entangle it 3) Long threads with spines or poison barbs to ensnare and stun prey

Coral Reef

-colonial forms of jellyfish make up ____________.

Class Anthozoa

-corals, sea fans, sea anenomes -Most advanced cnidarians, complex body -Symbiotic photosynthetic dinoflagellates, so limited to shallow water (Dinoflagellates need to be close to surface to absorb light)

Ephyra

-during the lifecycle, polyps bud off and form _________.

Primitive Senses

-eyespots, statocysts, mechanical and chemical receptors -Mostly small -Hence can rely on diffusion for gas exchange and excretion

Mesoglea

-jelly in the space between ectoderm and endoderm

Cnidarian Movement

-move by means of primitive muscle fibers arranged in two directions -Circular muscles can contract the exposed body -Longitudinal muscles can stretch the body out, bend the body in any direction -combination of these muscles leads to the smooth movements of all higher animals

Dimorphic

-sessile polyps or motile medusa -Both forms alternate in the life cycle -Both are diploid, so not true alternation of generations -Medusa is the sexual stage

Planula Larvae

External fertilization -Zygote develops into ______________. Larvae mature into new polyp

Colonial Forms

Many colonial forms - Obelia, Physalia Colonial forms have specialized feeding polyps and reproductive polyps Physalia - Portuguese Man of War, bell is dead medusa, inflated by numerous individual polyps hanging beneath